how can I read a specific line from a file?
user.txt:
root
admin
me
you
When I do
def load_user():
file = open("user.txt", "r")
nextuser_line = file.readline().strip()
print(nextuser_line)
file.close()
root will be printed, but I would like to read admin from the file. So I try to read the next line index using [1]
def load_user():
file = open("user.txt", "r")
nextuser_line = file.readline().strip()
print(nextuser_line[1])
file.close()
instead of printing 'admin', the output is 'o' from 'root', but not the next line from the file.
what am I doing wrong?
readline() reads the first line. To access lines through index, use readlines():
def load_user():
file = open("user.txt", "r")
lines = file.readlines()
print(lines[1])
file.close()
>>> load_user()
'admin'
To remove the \n from the lines, use:
lines = [x.strip() for x in file]
Related
So,I have this problem,the code below will delete the 3rd line in a text file.
with open("sample.txt","r") as f:
lines = f.readlines()
del lines[2]
with open("sample.txt", "w+") as f2:
for line in lines:
f2.write(line)
How to delete all lines from a text file?
Why use loop if you want to have an empty file anyways?
f = open("sample.txt", "r+")
f.seek(0)
f.truncate()
This will empty the content without deleting the file!
I think you to need something like this
import os
def delete_line(original_file, line_number):
""" Delete a line from a file at the given line number """
is_skipped = False
current_index = 1
dummy_file = original_file + '.bak'
# Open original file in read only mode and dummy file in write mode
with open(original_file, 'r') as read_obj, open(dummy_file, 'w') as write_obj:
# Line by line copy data from original file to dummy file
for line in read_obj:
# If current line number matches the given line number then skip copying
if current_index != line_number:
write_obj.write(line)
else:
is_skipped = True
current_index += 1
# If any line is skipped then rename dummy file as original file
if is_skipped:
os.remove(original_file)
os.rename(dummy_file, original_file)
else:
os.remove(dummy_file)
How to fetch the second line data from text file in Python.
I have a text file and in file there are some data in line by line_
Dog
Cat
Cow
How to fetch the second line which is “Cat” and store in a variable in python
var = # “Cat”
You should place the text file in the same directory with your Python code, which could be the following:
with open("animals.txt", "r") as f:
animals = [line.strip() for line in f]
second_line = animals[1]
Now, the variable "second_line" contains the data you want.
You can open a file, then read line by line while counting the line number as follows:
if __name__ == '__main__':
input_path = "data/animals.txt"
var = None
with open(input_path, "r") as fin:
n_lines = 0
for line in fin:
n_lines += 1
if 2 == n_lines:
var = line.strip()
break
print(var)
Result:
Cat
If the file is big, you may avoid reading all file and use readline to read one line twice:
with open ('file.txt') as file:
line = file.readline()
line = file.readline()
print(line)
...or check 'seek' method to start reading at specific character index.
Text file contains below data:
InitialSearch='Searched data'
file = open("textfile.txt","r")
lines = file.readlines()
file.close()
fileOutput = open ('NewTextFile.txt', 'w')
for x,line in enumerate(lines):
if line.find(InitialSearch)>=0:
fileOutput.write(line)
fileOutput.close
Code is not properly working
You already have the index of the "matched" line in your for loop. Just add two to it, and you will have the row you want to add to the output file.
InitialSearch='Searched data'
file = open("textfile.txt","r")
lines = file.readlines()
file.close()
with open('NewTextFile.txt', 'w') as fileOutput
for x,line in enumerate(lines):
if line.find(InitialSearch)>=0:
fileOutput.write(lines[x+2])
I want to append some text to every line in my file
Here is my code
filepath = 'hole.txt'
with open(filepath) as fp:
line = fp.readline()
cnt = 1
while line:
#..........
#want to append text "#" in every line by reading line by line
text from .txt file
line = fp.readline()
cnt += 1
You can read the lines and put them in a list. Then you open the same file with write mode and write each line with the string you want to append.
filepath = "hole.txt"
with open(filepath) as fp:
lines = fp.read().splitlines()
with open(filepath, "w") as fp:
for line in lines:
print(line + "#", file=fp)
Assuming you can load the full text in memory, you could open the file, split by row and for each row append the '#'. Then save :-) :
with open(filepath, 'r') as f: # load file
lines = f.read().splitlines() # read lines
with open('new_file.txt', 'w') as f:
f.write('\n'.join([line + '#' for line in lines])) # write lines with '#' appended
I'll assume the file is small enough to keep two copies of it in memory:
filepath = 'hole.txt'
with open(filepath, 'r') as f:
original_lines = f.readlines()
new_lines = [line.strip() + "#\n" for line in original_lines]
with open(filepath, 'w') as f:
f.writelines(new_lines)
First, we open the file and read all lines into a list. Then, a new list is generated by strip()ing the line terminators from each line, adding some additional text and a new line terminator after it.
Then, the last line overwrites the file with the new, modified lines.
does this help?
inputFile = "path-to-input-file/a.txt"
outputFile = "path-to-output-file/b.txt"
stringToAPpend = "#"
with open(inputFile, 'r') as inFile, open(outputFile, 'w') as outFile:
for line in inFile:
outFile.write(stringToAPpend+line)
I have a file which contains a user:
Sep 15 04:34:31 li146-252 sshd[13326]: Failed password for invalid user ronda from 212.58.111.170 port 42579 ssh2
Trying to use index method for string to edit the user within the file. So far I am able to print the user but now to delete and put in the new user.
newuser = 'PeterB'
with open ('test.txt') as file:
for line in file.readlines():
lines = line.split()
string = ' '.join(lines)
print string.index('user')+1
Do you want to update the file contents? If so, you can update the user name, but you will need to rewrite the file, or write to a second file (for safety):
keyword = 'user'
newuser = 'PeterB'
with open('test.txt') as infile, open('updated.txt', 'w') as outfile:
for line in infile.readlines():
words = line.split()
try:
index = words.index(keyword) + 1
words[index] = newuser
outfile.write('{}\n'.format(' '.join(words)))
except (ValueError, IndexError):
outfile.write(line) # no keyword, or keyword at end of line
Note that this code assumes that each word in the output file is to be separated by a single space.
Also note that this code does not drop lines that do not contain the keyword in them (as do other solutions).
If you want to preserve the original whitespace, regular expressions are very handy, and the resulting code is comparatively simple:
import re
keyword = 'user'
newuser = 'PeterB'
pattern = re.compile(r'({}\s+)(\S+)'.format(keyword))
with open('test.txt') as infile, open('updated.txt', 'w') as outfile:
for line in infile:
outfile.write(pattern.sub(r'\1{}'.format(newuser), line))
If you want to change the names in your log, here is how.
file = open('tmp.txt', 'r')
new_file = []
for line in file.readlines(): # read the lines
line = (line.split(' '))
line[10] = 'vader' # edit the name
new_file.append(' '.join(line)) # store the changes to a variable
file = open('tmp.txt', 'w') # write the new log to file
[file.writelines(line) for line in new_file]